Storage layer, conversion layer and a device for reading x-ray information, in addition to an x-ray cassette

ABSTRACT

The invention relates to a storage layer ( 4 ) for storing x-ray information, comprising a large number of needle-shaped storage material areas ( 15 A to  15 L) for guiding light radiation ( 17  to  28, 30  to  35 ). An absorption zone ( 14 A to  14 N), which contains absorption material for absorbing light radiation ( 17  to  23, 30  to  35, 39 ) lies between the individual needle-shaped storage material areas ( 15 A to  15 L) and absorbs less than all of the light radiation that it receives. The invention also relates to a device for reading x-ray information from a storage layer of this type and to an x-ray cassette which has a device of this type for reading x-ray information.

BACKGROUND OF THE INVENTION

The present invention relates to a storage layer for storing and aconversion layer for storing and converting x-ray information which hasa multitude of needle-shape storage material areas as well as a devicefor reading x-ray information from a storage layer and an x-ray cassettetherefor.

In particular for medical purposes, an image is generated by x-radiationof an object, for example, of a patient, where the image is stored in astorage layer as a latent image. Thus, such an x-radiation imagecontains x-ray information about the object. To read the x-rayinformation stored in the storage layer, it is excited using a radiationsource. Due to this excitation, the storage layer emits light thatexhibits an intensity that corresponds to the x-ray information storedin the storage layer. The light emitted by the storage layer is receivedby a receiving means such that the x-ray information stored in thestorage layer can then be made visible. For example, the x-rayinformation can be displayed directly on a monitor. Typically, suchstorage layers are applied to a carrier material that can be eithertransparent or reflecting. With a reflecting carrier material, both theradiation source and the receiving means are arranged on the same sideof the carrier material, that is, on that side of the carrier materialwhere the storage layer is located. If the storage material is locatedon a transparent carrier material, then the radiation source is locatedon one side of the carrier material, and the receiving means on theopposite side of the carrier material. This arrangement has theparticular advantage that a larger amount of the radiation emitted bythe storage layer can be captured by the receiving means. A betterreproduction quality of the x-ray information stored in the storagelayer is, therefore, possible.

For example, from the patent document DE 198 59 747 C1 it is known touse a special storage layer for storing x-ray information, where thestorage layer exhibits a special crystallite, needle-shaped structure.The special storage layer exhibits numerous “needles” that can serve thepurpose of guiding both the excitation and the emission radiation.Crystalline “needles” are cultivated for such storage layers. Such aneedle storage layer is constructed of binary alkali halides, such ascesium bromides, CsBr. These structured alkali halides can be doped withsuitable activators such as gallium, thallium, europium, etc. Dependingon their given purpose, the individual needle crystals vary in heightbetween 100 and 600 μm and have a thickness of about 10 μm. Typically,the individual needles are separated from one another by a small airgap. Both the excitation and the emission lights are guided in theindividual needles that serve as light conductors according to theprinciple of total reflection. Incident excitation radiation thatarrives at a certain angle is largely transmitted without scatteringuntil it strikes an information center in the crystal lattice of theneedle, where the x-ray information is stored. The emission radiationthat is generated through the excitation of the information center istransferred in the respective needle and is guided out of this needlesuch that it can be detected by the receiving means. Such aneedle-shaped storage layer is known, in particular, from the Europeanpatent application EP 0 751 200 A1. Using this special storage layerreduces scattering of the excitation radiation within the storage layer.In particular, when reading the x-ray information that is stored in thestorage layer line by line, scattering of the excitation radiationperpendicular to the direction of the lines is disadvantageous becauseinformation centers may be excited that belong to a line of the storagelayer other than the one that is being read at the moment. In thismanner, emission radiation may get “lost”; i.e., it cannot be detectedby the receiving means. In addition, scattering of the emissionradiation within the storage layer is reduced with the result that inparticular a good local resolution is achieved for the detection of theemission radiation in the receiving means. However, it has been foundthat, for example, excitation radiation that enters the storage layer atan incident angle that is greater than a certain angle does not remainin the respective needles but instead passes perpendicular through theseneedles. Especially because these needles exhibit an irregular outerstructure, scattering of the excitation radiation can occur that isdisadvantageous for the quality of the reproduction of the x-rayinformation. Since, in particular, the irregular outer structure of theneedles results in a portion of the excitation radiation not being fullyreflected in the needle, a blurring is created in the reproduction ofthe x-ray information. A similar situation applies to the emissionradiation that is essentially emitted isotropically by an informationcenter that is struck by the excitation radiation. Due to the apertureangle that is determined by the relation between the refractive index ofair to the alkali halide of which the individual needles have beencultivated, a portion of the emission light is not fully reflected inthe needle but instead is emitted from the respective needle. This leadsto a corresponding degradation of the local resolution when detectingthe emission radiation.

Alternatively to the interim storing of x-ray information in the storagelayer, as described above, x-ray information that is contained in thex-radiation can also be converted directly into light radiation using aconversion layer. This light radiation that contains an image of thex-ray information can then be detected by a light-sensitive sensor andconverted into electrical signals. Such a conversion layer and a devicewhere such a coating is used are known, for example, from the patentdocuments DE 195 05 729 C1, DE 195 06 809 A1 or DE 195 09 021 C2. Theconversion layer for converting the x-radiation into light radiation isdesignated as a so-called scintillator layer that may consistessentially of cesium iodide CsI. X-ray detectors that contain suchconversion layers are already available on the market today. Forexample, the company Trixell, 460 Rue de Pommarin, 38430 Moirans,France, uses such a conversion layer in their product Pixium 4600. Theseconversion layers for converting x-radiation into light radiationcontain numerous conversion zones with materials that directly convertx-radiation into light radiation. Similar to the storage layersdescribed above, these conversion zones are arranged in the conversionlayers in needle-shape next to one another. This means that theconversion of x-radiation to light radiation occurs in the individualneedles. The light energy, which has a low energy in comparison to thex-radiation, can exit a needle where it was generated due to theaperture angle at the barrier layers of the needles and can arrive atone or more other needles. This has the result that light radiation thathas been generated in a certain needle exits that conversion layer at anentirely different location, and is therefore detected by thelight-sensitive sensor at a location that does not correspond to thelocation of the needle where the light radiation was generated. As wasthe case previously with the storage layers, the local resolution isfalsified during the detection of the light radiation that is emitted bythe conversion layer due to the described scattering.

SUMMARY OF THE INVENTION

It is, therefore, the objective of the present invention to specify astorage layer and a conversion layer, as well as a device for readingx-ray information, and an x-ray cassette therefor, such that a goodquality is possible when reproducing x-ray information.

At the storage layer according to the invention, an absorption layer forabsorbing light radiation is located between the individualneedle-shaped storage material areas. Correspondingly, an absorptionmaterial for absorbing light radiation is located between theneedle-shaped conversion material areas of the conversion material zonesaccording to the invention.

Based on the present invention, light rays, i.e., excitation and/oremission radiation which exit on the sides of the needles due to theaperture angle as determined by the used materials, are absorbed. As aresult, the overall amount of light radiation that enters from oneneedle into one or more adjacent needles is reduced. Thus, thescattering of the light radiation can be kept low such that thesharpness of the x-ray image that is reproduced from the stored orconverted x-ray information is improved. Here, aperture angle refers tothat angle up to which a total reflection of the excitation or emissionradiation occurs in the storage layer. After creating the needle-shapedstorage or conversion layer, an absorption material can be filledbetween the cultivated needles. Undesired absorption material that maybe present on the surface of the storage or conversion layer after ithas been poured in the spaces between the needles can be removed bysubsequent polishing or grinding of the surface. Such removal of theabsorption material can also be carried out using chemical methods. Tothis end, the surface of the storage or conversion layer isadvantageously pretreated such that the adhesion of the absorptionmaterial is very weak. With the storage layer, the stimulation radiationfor exciting the information centers of the storage layer can enterunhindered into the storage layer due to the removal of the absorptionmaterial from the surface. Furthermore, the emission radiation can exitundampened from the storage layer. This is particularly advantageous forthe storage layer because it has a lower-energy stimulation radiationthan the x-radiation that strikes the conversion layer directly and isconverted into light radiation.

In an advantageous embodiment of the invention, two absorption zones arepresent between two adjacent needle-shaped storage material areas withan air layer between the two the absorption layers. Thus, the air layerseparates the two absorption zones from one another. If an absorptionzone with an absorption material borders a storage material area, thenthe aperture angle is reduced in comparison to the case, where airborders the storage material areas. This means that a smaller amount ofexcitation and emission radiation is fully reflected within theneedle-shaped storage material areas. A larger amount of excitation andemission radiation exits the storage material areas. This radiationexiting the storage material areas is, at least partially, absorbed inthe absorption zone. However, it cannot be fully avoided that radiationalso penetrates the absorption zones and that it is not totally absorbedin these areas. By having advantageously an air layer introduced betweentwo absorption zones, an additional portion of the light exiting theneedle-shaped storage material area is again reflected at the barrierlayer—due to the large aperture angle at this transition. This reflectedlight is then again, at least partially, absorbed in the absorption zonethat it has been reflected back to. In this manner, the amount ofscatter radiation that exits a storage material and enters one or moreadjacent storage material areas is reduced even further. Thisadvantageous design of the absorption zones can be appliedcorrespondingly to the conversion layers.

In one particularly advantageous embodiment of the invention, the lightradiation, i.e., the stimulation and/or emission radiation, entering theabsorption zone by means of the absorption material, is not fullyabsorbed but only to an amount that is smaller than the respective fullstimulation and/or emission radiation entering the absorption zone. Thisadvantageously ensures that the amount of emission radiation exiting thestorage layer is greater than with a full absorption of the lightradiation.

In an additional advantageous embodiment, the absorption materialcontains pigments. Such pigments are in an ideal manner well suited toabsorb the excitation radiation and the emission radiation, whichtypically have wavelength in the visible range of the spectrum. Toabsorb the excitation radiation, which is typically in the redwavelength range of the spectrum, blue pigments are particularly wellsuited. To absorb emission radiation that is typically in the bluewavelength range of the spectrum, red pigments are particularly wellsuited. This advantageous design of the absorption zones iscorrespondingly applicable for the conversion layer as well.

In an additional advantageous embodiment of the invention, the pigmentsare dissolved in a solvent. Since the storage material areas containalkali halides, which are typically water-soluble inorganic crystals,preferably an organic solvent should be used.

Due to the high water solubility of the crystals of the storage materialareas, it is also recommended to dry the pigments and thus to eliminatea potential water portion.

This advantageous embodiment of the absorption zone is correspondinglyapplicable for the conversion layer as well.

For a full understanding of the present invention, reference should nowbe made to the following detailed description of the preferredembodiments of the invention as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary application of a device according to theinvention for reading x-ray information from a storage layer accordingto the invention.

FIG. 2 is a schematic presentation of an exemplary application of anarrangement with a conversion layer according to the invention.

FIG. 3 shows a first preferred embodiment of a storage layer accordingto the invention with an exemplary course of excitation beams.

FIG. 4 shows a second preferred embodiment of the storage layeraccording to the invention with an exemplary presentation of the courseof emission beams.

FIG. 5 shows a third preferred embodiment of a storage layer accordingto the invention, where the absorption zones exhibit an air layerbetween the needles.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the present invention will now be describedwith reference to FIGS. 1–5 of the drawings. Identical elements in thetwo figures are designated with the same reference numerals.

FIG. 1 shows an exemplary embodiment of a device 1 according to theinvention for reading x-ray information from a storage layer. In thepresent exemplary embodiment, this device is an x-ray cassette 1. Thex-ray cassette 1 contains a storage layer 4 as well as a reader head 2for reading x-ray information that is stored in the storage layer 4. Forthis purpose, the reader head 2 includes a radiation source (not shown)for exciting the storage layer and a receiving means (not shown) forreceiving the emission radiation emitted by the storage layer 4 due tothe excitation. Here, the radiation source is designed as a line lightsource and contains numerous laser diodes arranged next to one another.With these laser diodes, a line of the storage layer 4 can be excited.Such a line stretches along a direction B essentially across the entirewidth of the storage layer 4. In place of the line light source equippedwith laser diodes, a different light source that is suitable forexciting the storage layer 4 can be used as well. For example, aso-called “flying spot” radiation source may be used where a laser beamemitted by a laser device is directed to a pivoted polygon mirror. Thepolygon mirror rotates such that the laser beam is guided across a lineof the storage layer 4, whereby one individual point of the line isexcited at a time. The receiving means contained in the reader head 2may contain a so-called “charge-coupled-device” (CCD) cell that is usedfor receiving the emission radiation emitted by the storage layer 4. TheCCD cell includes numerous photo detectors arranged in a line parallelto one another. With these photo detectors, a photoelectric conversionof the received emission radiation can be performed. A fixed connectionis established between the line light source and the CCD cell such thatthe image of the x-ray information stored in the storage layer 4, i.e.,the excitation of the storage layer and the reception of the radiationemitted due to the excitation are precisely harmonized with one anothersuch that a precise assignment is ensured even during the actual readingprocedure. The entire reader head 2 for reading the information storedin the storage layer 4 can be moved via a drive means (not shown), whichmay be a linear motor, in a movement direction A. This can generate anadvance in order to read the entire storage layer 4 using theline-by-line excitation and detection. To guide the reader head 2 forreading the storage layer 4, the x-ray cassette 1 includes two guidebars 3 along the two longitudinal sides of the storage layer 4. Thestorage layer 4 is a storage layer that exhibits a crystallite,needle-shaped structure. Absorption zones that contain an absorptionmaterial for absorbing light radiation are present between theindividual needles of the storage layer 4.

FIG. 2 shows an example of an arrangement that includes a conversionlayer 6 for converting x-radiation into light radiation. The conversionlayer 6 is a so-called scintillator layer. This scintillator layer ispart of a conversion means 5 that additionally includes an opticalimaging means 7 and an opto-electronic image converter. The scintillatorlayer 6, the optical imaging means 7 and the image converter 8 aredesigned in a plane and are arranged directly behind one another in theconverter means 5. The scintillator layer 6 contains numerouscrystalline needle-shaped converter material areas, where thex-radiation entering these areas is converted to light radiation. Theconverter material areas of the scintillator layer 6 may consist, forexample, of cesium iodide, CsI, which in turn can be doped. In itsneedle-shaped structure, the scintillator layer corresponds to a largeextent to the structure of the storage layer 4 (FIG. 1). Absorptionzones with absorption material for absorbing light radiation that isgenerated due to the x-radiation are present between the individualneedle-shaped converter material areas of the scintillator layer 6. Theoptical imaging means 7 can contain, for example, an array with numerousmicro-lenses. This micro-lens array reproduces the light radiationemitted by the scintillator layer 6 on the image converter 8. The imageconverter 8 contains numerous light-sensitive sensors that convert thereproduced light radiation to corresponding electrical signals. Theimage converter 8 may consist of hydrogenous, amorphous silicon (aSi:H).An x-radiation 11 emitted by an x-ray cannon strikes the scintillatorlayer 6. The x-radiation with the x-ray information is converted tolight radiation corresponding to the x-ray information in thisscintillator layer 6. The image converter 8 generates electrical signalscorresponding to the information contained in the light radiation. Theimage converter 8 is connected to a control means 9 that is providedwith the electrical signals from the image converter. The control means9 performs image processing such that the x-ray information cansubsequently be presented on a monitor 10 that is connected to thecontrol means 9. A reading of stored x-ray information as is requiredusing the x-ray cassette according to FIG. 1. is not necessary whenusing the conversion means 5 according to FIG. 2. Instead, thex-radiation 11 can be converted directly in order to present the x-rayinformation contained in it on a monitor 10.

FIG. 3 shows a presentation of a reader head with a radiation source 12and a receiving means 13 along the advance direction A of the readerhead. The storage layer 4 is located between the radiation source 12 andthe receiving means 13. FIG. 3 shows schematically a section through thestorage layer 4 along the advance direction A of the reader head withthe radiation source 12 and the receiving means 13. The storage layer 4contains numerous needle-shaped storage areas arranged next to oneanother. FIG. 3 shows a first needle-shaped storage area 15A with asecond needle-shaped storage area 15B arranged adjacent to it, and inturn, a third needle-shaped storage area 15C arranged next to the secondstorage area. Absorption zones that contain an absorption material forabsorbing light radiation are present between the respectiveneedle-shaped storage areas 15A to 15C. A first absorption zone 14A islocated at the left side of the first storage area 15A. The absorptionmaterial is indicated in this first absorption zone 14A representativefor the remaining absorption zones—also of the subsequent preferredembodiments. The absorption material contains a solvent 38 that containsnumerous pigments 37. Advantageously, these pigments are of such a colorthat either the excitation radiation emitted by the radiation source 12or the emission radiation emitted by the respective needle-shapedstorage areas due to the excitation with the excitation radiation can beabsorbed. To this end, the pigments 37 are preferably of a red or of ablue color. The blue color can be used in particular to absorb theexcitation radiation emitted by the radiation source 12. The red colorparticles 37 can in particular absorb the emission radiation. Otherabsorption materials can be used in place of the color particles 37 andthe solvent 38; in particular, the color particles 37 can also exhibitother colors than red and blue, as long as these colors are suited forabsorbing excitation radiation and/or emission radiation. A one hundredpercent absorption of excitation and emission radiation, as could beachieved, for example, using black pigments in the absorption material,is here not desired, because too large a quantity of excitation andemission radiation would be absorbed, which would lead to too small aportion of the emission radiation being able to exit the storage layer4. Certain blurriness when detecting the emission radiation exiting thestorage layer 4 is, therefore, accepted in order to keep the intensityof the emission radiation that exits the storage layer 4 at a certainlevel. Advantageously, the absorption material can be designed such thatonly a certain amount of the intensity of the excitation or emissionradiation is absorbed in the respective absorption zones.

At least a portion of the respective excitation or emission radiationis, therefore, fully absorbed only after passing through severalabsorption zones. In this manner, it is possible to set optimalabsorption properties of the absorption material with regard to theintensity of the emission radiation exiting from the storage layer 4while accepting a certain blurriness.

A second absorption zone 14B is present between the first needle-shapedstorage area 15A and the second storage area 15B. A third absorptionzone 14C is present in the storage layer 4 between the second storagearea 15B and the third storage area 15C.

Numerous information centers are present in the storage areas 15A to 15Cdue to the irradiation with x-radiation. The entirety of the informationcenters and in particular their local positions in the storage layer 4corresponds to the stored x-ray information. Serving as examples, someinformation centers are indicated in FIG. 3 by dark circles. Arepresentative information center with the reference character 16A isdesignated in the second storage area 15B, and an additionalrepresentative information center with the reference character 16B isdesignated in the third storage area 15C.

A first excitation beam 17, a second excitation beam 18 and a thirdexcitation beam 19 are shown in FIG. 3 representative for numerousexcitation radiations that are emitted by the radiation source 12. Thefirst excitation beam 17 enters the second storage area 15B and therestrikes the information center 16A. Due to the excitation of theinformation center 16A by the first excitation beam 17, the storage area15B emits an emission beam 20. This emission beam 20 is shown hererepresentative of numerous emission beams that are largely emittedisotropically from the information center 16A. As presented in FIG. 3,the emission beam 20 exits the second storage area 15B and strikes thereceiving means 13. The second excitation beam 18 also enters the secondstorage area 15B and there strikes the barrier layer to the secondabsorption zone 14B. This striking of the barrier layer occurs under acertain angle that is smaller than the aperture angle, which isdetermined by the refractive indices of the storage area material andthe absorption material. A total reflection occurs at the barrier layersuch that the second stimulation beam is reflected back into the secondstorage area 15B. Since the second excitation beam 18 reflected in thismanner does not strike an information center in the second storage area15B, it strikes the barrier layer to the third absorption zone 14C.Since the angle under which the second excitation beam strikes thisbarrier layer to the third absorption zone 14C is greater than theaperture angle, total reflection does not occur. Thus, the secondexcitation beam 18 enters the third absorption zone 14C and is thereabsorbed by the pigments contained in it, such that it cannot exit thethird absorption zone 14C to enter the third storage area 15C. The thirdexcitation beam 19 also enters the second storage area 15B and therestrikes the barrier layer to the second absorption layer 14B under acertain angle. This angle under which the third excitation beam 19strikes the barrier layer is smaller than the aperture angle, such thatthe third excitation beam 19 is reflected into the second storage area15B. Since the third excitation beam on its path through the secondstorage area 15B also does not strike an information center, it arrivesat the barrier layer to the third absorption zone 14C. The thirdexcitation beam 19 strikes this barrier layer at an angle that isgreater than the aperture angle. Thus, a total reflection does not occurat the barrier layer, and the third excitation beam enters the thirdabsorption zone 14C. The third excitation beam 19 is not absorbed in thethird absorption zone 14C. In fact, the third excitation beam 19 passesthrough the third absorption zone 14C and enters the third storage area15C. In the third storage area 15C, the third excitation beam 19 finallystrikes the information center 16B. The excitation of the informationcenter 16B by the third excitation beam 19 results in additionalemission beams, being emitted, essentially isotropically, by thisinformation center 16B. As a representative example, an emission beam 39that emits from the information center 16B is shown in FIG. 3. Thedirection of propagation of this emission beam 39 indicates that it willexit the third storage area 15C without being able to be detected by thereceiving means 13. Thus, at least a portion of the informationcontained in the information center 16B cannot be detected by thedetection means 13. Thus, an information loss occurs due to thescattering of the third excitation beam 19 into the third storage area15C. Thus, FIG. 3 shows, in particular through the courses of the secondand third excitation beams 18 and 19, how the advantageous absorptioneffect of the absorption zones between the individual needle-shapedstorage areas has a positive effect on reading the x-ray information.The absorption zones prevent that at least a portion of the excitationradiation passes over into adjacent storage areas, where they thenstrike information centers present in the adjacent storage areas, whichthen emit emission radiation due to the excitation radiation, where alocation-accurate emission radiation cannot be detected by the receivingmeans 13.

FIG. 4 shows a second exemplary embodiment of the reader head and thestorage layer according to FIG. 3. Here, the reader head with theradiation source 12 and the receiving means 13 as well as the storagelayer 4 are shown in a direction of propagation B of a line of thestorage layer 4 that is excited by the radiation source 12. FIG. 4 showsschematically a section through the storage layer 4 along the directionB. The storage layer 4 presented in FIG. 4 exhibits a fourthneedle-shaped storage area 15D and arranged adjacent to it, a fifthneedle-shaped storage area 15E. A fourth absorption zone 14D is locatedbetween the fourth storage area 15D and the fifth storage area 15E.

To the right of the fifth needle-shaped storage area 15E is a sixthneedle-shaped storage area 15F. Located between the fifth and the sixthstorage areas 15E and 15F is a fifth absorption zone 14E. To the rightof the storage area 15F is a seventh needle-shaped storage area 15G ofthe storage layer 4. Located between the sixth storage area 15F and theseventh storage area 15G is a sixth absorption zone 14F. In the fifthstorage area 15E and the sixth storage area 15F, blackened circles againindicate information centers that contain x-ray information. As arepresentative example, one of these information centers in the fifthstorage area 15E is designated with the reference character 16C.

During operation, the radiation source 12 emits numerous excitationbeams in the direction of the storage layer 4. As representativeexamples for these numerous excitation beams, two excitation beams 21are presented in the exemplary embodiment according to FIG. 4. Here,these two excitation beams 21 enter the fifth storage area 15E and bothstrike the information center 16C. Numerous emission beams are,essentially isotropically, emitted from the information center 16C dueto the excitation of the information center 16C by the two excitationbeams 21. Representative for the multitude of emission beams are shown asecond emission beam 22, a third emission beam 23, a fourth emissionbeam 24, a fifth emission beam 25, a sixth emission beam 26, a seventhemission beam 27 and an eight emission beam 28. In the following, thecourses of the emission beams 22 to 28 shall clarify the mode of actionof the absorption zones 14D to 14F.

The second emission beam 22 runs directly from the information center16C through the fifth storage area 15E in the direction of the receivingmeans 13. The emission beam 22 is detected by the receiving means 13.The third emission beam 23 runs—beginning at the information center16C—also through the fifth storage area 15E in the direction of thereceiving means 13. The third emission beam 23, however, strikes thebarrier layer of the fifth storage area 15E and the fifth absorptionzone 14E prior to exiting the storage layer 4. The angle under which thethird emission beam 23 strikes this barrier layer is smaller than theaperture angle, which is determined by the refractive indices of thematerials of the fifth storage area 15E and the fifth absorption zone14E. Thus, a reflection of the third emission beam 23 occurs at thebarrier layer. The reflected third emission beam 23 initially remains inthe fifth storage area 15E and subsequently exits the storage area andtherefore the storage layer 4, and is then captured by the receivingmeans 13. The fourth emission beam 24 runs—beginning at the informationcenter 16C—also initially through the fifth storage area 15E, and thenstrikes the barrier area of the fifth storage area 15E to the fourthabsorption zone 14D. Since the angle with which the fourth emission beam24 strikes this barrier layer to the fourth absorption zone 14D isgreater than the aperture angle, a reflection of the fourth emissionbeam 24 does not occur at the barrier layer. In fact, the fourthemission beam 24 enters the fourth absorption zone 14D. However, thefourth emission beam 24 is not absorbed in the fourth absorption zone14D. The emission beam 24 passes through the absorption zone 14D andenters the fourth storage area 15D. A location-accurate detection of thex-ray information that is transported by the fourth emission beam 24 is,therefore, not possible with the receiving means 13. A differentsituation occurs with the fifth emission beam 25. It runs—beginning atthe information center 16C—initially also through the fifth storage area15E, and then strikes the barrier layer between the fifth storage area15E and the fifth absorption zone 14E. Because the angle, under whichthe emission beam 25 strikes this barrier layer, is also greater thanthe aperture angle, no reflection of the emission beam 25 occurs at thebarrier layer. In fact, the emission beam enters the fifth absorptionzone 14E. Contrary to the fourth emission beam 24, the fifth emissionbeam 25 is, however, absorbed in the fifth absorption zone 14E. It doesnot enter from the fifth absorption zone 14E into the adjacent sixthstorage area 15F. A location-inaccurate detection of the emission beam25 by the receiving means 13 is, therefore, not possible. The same takesplace with the eighth emission beam 28. It too enters—beginning at theinformation center 16C—the fifth absorption zone 14E and is thenabsorbed by it. The eighth emission beam 28 does not enter into thesixth storage area 15F. Thus, the absorbed eighth emission beam 28 alsodoes not contribute to the location blurriness.

Also the sixth emission beam 26—beginning at the information center16C—strikes the barrier layer between the fifth storage area 15E and thefifth absorption zone 14E. Here, the angle under which the sixthemission beam 26 strikes the barrier layer is greater than the apertureangle. Thus, the sixth emission beam is not reflected at the barrierlayer to the fifth absorption zone 14E. In fact, the sixth emission beam26 enters into the fifth absorption zone 14E, passes through it and thenarrives at the sixth storage area 15F. Thus, the emission beam 26 hasnot been absorbed in the fifth absorption zone 14E. The emission beam 26passes through the sixth storage area 15F and arrives at the barrierlayer between the sixth storage area 15F and the sixth absorption zone14F. Here too, the angle under which the emission beam 26 strikes thisbarrier layer is greater than the aperture angle, such that again noreflection occurs. Rather, the emission beam 26 enters the sixthabsorption zone 14F, passes through it and arrives at the seventhstorage area 15G. Thus, the sixth emission beam 26 is not absorbed inthe sixth absorption zone 14F. It is again different with the seventhemission beam 27. Similar to the sixth emission beam 26, ittoo—beginning at the information center 16C—passes through the fifthabsorption zone 14E and the sixth storage area 15F. Thereafter, it toostrikes the barrier layer between the sixth storage area 15F and thesixth absorption zone 14F. Because the angle under which the emissionbeam 27 strikes this barrier layer is again greater than the apertureangle, no reflection occurs at the barrier layer. The emission beam 27enters into the sixth absorption zone 14F, where it is absorbed,contrary to the emission beam 26. The emission beam 27 does then notcontinue through the absorption zone 14F into the seventh storage area15G. One can recognize that the sixth absorption zone 14F contributes tothe avoidance of additional location blurriness due to a continueddistribution of the seventh emission beam 27.

FIG. 5 shows a third preferred embodiment of the storage layer 4 thatcontains x-ray information. In this example, the x-ray information isalso read using a reader head, which includes the radiation source 12and the receiving means 13. FIG. 5 shows the presentation of theradiation source 12, the receiving means 13 and the storage layer 4,which is arranged between these two, in the direction of propagation Bof a line of the storage layer 4, which is excited using the radiationsource 12. FIG. 5 schematically shows a section through the storagelayer 4 along the direction B.

The section of the storage layer 4 presented in FIG. 5 shows an eighthneedle-shaped storage area 15H, a ninth needle-shaped storage area 15K,a tenth needle-shaped storage area 15L and an eleventh needle-shapedstorage area 15M. Absorption zones that contain absorption material forabsorbing the light radiation are present between these four storageareas 15H to 15M. Contrary to the embodiments of FIGS. 3 and 4, here,air gaps are introduced into these absorption zones. Thus, a seventhabsorption zone 14G and an eighth absorption zone 14H are presentbetween the eighth storage area 15H and the ninth storage area 15K.These two absorption zones 14G and 14H in turn are separated from oneanother by an air gap 29A. The air gap 29A contains an air layer.Corresponding to this arrangement is the situation between the ninthstorage area 15K and the tenth storage area 15L. A ninth absorption zone14K and a tenth absorption zone 14L are present between these twostorage areas 15K and 15L. These two absorption zones 14K and 14L inturn are separated from one another by an air gap 29B containing an airlayer. An eleventh absorption zone 14M and a twelfth absorption zone 14Nare present between the tenth storage area 15L and the eleventh storagearea 15M. These two absorption zones 14M and 14N are separated from oneanother by an air gap 29C containing an air layer.

To clarify the mode of operation of the air layers 29A to 29C, which arepresent between the individual absorption zones, the beam profiles ofexcitation and emission beams are described anew based on FIG. 5 in thefollowing. During operation, the radiation source 12 emits a multitudeof excitation beams in the direction of the storage layer 4. Theexcitation beam 30 is shown in FIG. 5 as a representative example forthe multitude of excitation beams. This excitation beam 30 enters theninth storage area 15K and there strikes an information center 16D. Dueto the excitation of the information center 16D by the excitation beam30, a multitude of emission beams are essentially isotropically emitted.FIG. 5 shows as representative examples of the multitude of emissionbeams a ninth emission beam 31, a tenth emission beam 32, an eleventhemission beam 33, a twelfth emission beam 34 and a thirteenth emissionbeam 35. The information center 16D emits the ninth emission beam 31 inthe direction of the receiving means 13. However, the emission beam 31strikes the barrier layer between the ninth storage area 15K and theninth absorption zone 14K. The angle under which the emission beam 31strikes this barrier layer is smaller than the aperture angle such thata reflection occurs at the barrier layer.

The reflected ninth emission beam 31 then continues through the ninthstorage area 15K, exits it and is then captured by the receiving means13. The aperture angle at the barrier layer between the ninth storagearea 15K and the ninth absorption zone 14K is, in turn, determined bythe refractive indices of the storage area material and the absorptionzone material.

The tenth emission beam 32 also runs—beginning at the information center16D—in the direction of the barrier layer toward the ninth absorptionzone 14K. However, since the angle under which the emission beam 32strikes this barrier layer is greater than the aperture angle, noreflection occurs; in fact, the tenth emission beam 32 enters the ninthabsorption zone 14K and, since it is not absorbed in the absorption zone14K, strikes the barrier layer between the ninth absorption zone 14K andthe air layer 29B. The tenth emission beam 32 is reflected at thisbarrier layer, because the angle under which the emission beam 32strikes this barrier layer to the air layer 29B is smaller than theaperture angle. This aperture angle is determined by the refractiveindices of the absorption material and air. The aperture angle betweenthe absorption material and air, called the air aperture angle, isgreater than the aperture angle between the absorption material and thestorage area material, called the material aperture angle. It is,therefore, possible that light beams strike a barrier layer at an anglethat is greater than the material aperture angle, such that reflectionsdo not occur, however that is smaller than the air aperture angle suchthat a reflection does occur at a barrier layer toward the air. Thus, byapplying the air layers 29A to 29C between the individual absorptionzones 14G to 14N, the light beams are absorbed in the absorption zones14G to 14N. At the same time, due to the air layers 29A to 29C, theaperture angle at the air layers 29A to 29C is enlarged versus thebarrier layers between the storage area material and the absorptionmaterial. This is especially made clear by the profile of the tenthemission beam 32. Although this tenth emission beam 32 enters into theabsorption zone 14K, it is reflected at the barrier layer to the airlayer 29B. This is the case because the aperture angle at the barrierlayer between the absorption zone 14K and the air layer 29B is greaterthan the aperture angle at the barrier layer between the storage area15K and the absorption zone 14K.

Furthermore, FIG. 5 shows the eleventh emission beam 33, which emitsfrom the information center 16D and enters into the absorption zone 14H.The eleventh emission beam 33 is absorbed in this absorption zone 14H,i.e., it is avoided that the emission beam 33 enters into anotherstorage material area. Contrary to this, the twelfth emission beam34—beginning at the information center 16D—enters the ninth absorptionzone 14K. The emission beam 34 passes through the absorption zone 14K aswell as the air layer 29B and the tenth absorption zone 14L, because theangle under which the beam 34 strikes each barrier layer is greater thanthe respective aperture angle. Thus, the emission beam 12 enters intothe tenth storage area 15L, passes through it until it strikes thebarrier layer to the eleventh absorption layer 14M. The beam isreflected at this barrier layer and passes through the tenth storagearea 15L in the direction of the receiving means 13. Finally, the beam34 exits the storage layer 4 and is captured by the receiving means 13.The thirteenth emission beam 35—beginning at the information center16D—passes through the ninth storage area 15K, the ninth absorption zone14K and the air layer 29B and enters the tenth absorption zone 14L. Thethirteenth emission beam 35 is absorbed in this tenth absorption zone14L. Thus, it is avoided that the thirteenth emission beam 35 furtherpropagates and that this emission bean exits the storage layer 4 and isdetected by the receiving means 13 at a location that is not in closeproximity to the original information center 16D.

There has thus been shown and described a novel storage layer andconversion layer, as well as a device for reading x-ray information andan x-ray cassette therefor which fulfills all the objects and advantagessought therefor. Many changes, modifications, variations and other usesand applications of the subject invention will, however, become apparentto those skilled in the art after considering this specification and theaccompanying drawings which disclose the preferred embodiments thereof.All such changes, modifications, variations and other uses andapplications which do not depart from the spirit and scope of theinvention are deemed to be covered by the invention, which is to belimited only by the claims which follow.

1. A storage layer for storing x-ray information comprising (a) amultitude of needle-shaped storage material areas for guiding excitationlight radiation and for producing emission light radiation in responsethereto, and (b) two absorption zones, with absorption material forabsorbing light radiation, disposed between the individual needle-shapedstorage material areas with an air layer present between these twoabsorption zones, said absorption material absorbing less than the totalamount of the excitation radiation that enters said absorption zones. 2.A storage layer as set forth in claim 1, wherein the absorption zonesare directly adjacent to needle-shaped storage material areas.
 3. Astorage layer as set forth in claim 1, wherein the absorption materialcontains pigments.
 4. A storage layer as set forth in claim 3, whereinthe pigments that are contained in the absorption material are dissolvedin a solvent.
 5. A storage layer as set forth in claim 3, wherein thepigments contain primarily blue pigments.
 6. A storage layer as setforth in claim 3, wherein the pigments contain primarily red pigments.7. A device for reading x-ray information from a storage layer accordingto claim 1, said device comprising a radiation source for exciting thestorage layer using excitation radiation and receiving means forreceiving emission radiation that is emitted from the storage layer dueto the excitation with the excitation radiation.
 8. An x-ray cassettecomprising a reading device as set forth in claim
 7. 9. A device as setforth in claim 1, wherein the absorption material is selected such thatthe excitation radiation is partially absorbed.
 10. A storage layer asset forth in claim 1, wherein said absorption material also absorbs lessthan the total amount of emission light radiation that enters saidabsorption zones.
 11. A device as set forth in claim 10, wherein theabsorption material is selected such that the emission radiation ispartially absorbed.